Ice Pops May Confound Tests After Transplant

Consumption of flavored ice pops could result in a false-positive test for galactomannan, which could have implications for the treatment of immunocompromised patients, a case report showed.

A 42-year-old woman with a myeloproliferative syndrome had negative galactomannan tests until about a month after a hematopoietic stem cell transplant, when the index spiked to 2.22 on day 32 and 3.01 on day 34 (0.5 or higher is considered positive), according to Nicolas Guigue, PharmD, of the Hôpital Saint Louis in Paris, and colleagues.

It turned out that the woman, who had no evidence of invasive aspergillosis infection, started eating three or four ice pops each day starting 29 days after the transplant, and that the ice pops contained galactomannan, they reported in a letter to the editor in the July 4 issue of the New England Journal of Medicine.

"Physicians should be aware of this unusual cause of interaction with the galactomannan test, which can result in unnecessary investigations and treatments," they wrote.

Galactomannan is found in the cell wall of Aspergillus and testing for it -- primarily in immunocompromised patients -- can detect invasive infections with the fungus.

The patient described in the case report had galactomannan tests performed twice a week starting on the day of the stem cell transplant. When the first positive tests came back about a month after the transplant, the woman had severe gastrointestinal graft-versus-host disease but no signs of infection with Aspergillus and no pulmonary or sinus symptoms.

After examining the patient's other intravenous treatments for an explanation for the positive galactomannan test result -- and coming up empty -- her doctors started her on voriconazole on day 35 after the transplant.

When the connection with the ice pops was made the patient stopped eating them, and within a week the galactomannan tests started coming back negative again.

The voriconazole was stopped on day 53. The patient eventually died from graft-versus-host disease and cytomegalovirus infection on day 141, but she had no signs of aspergillosis.

To further examine the interaction between ice pops and false-positive galactomannan tests, the researchers tested 37 ice pops from three different brands. They also checked for fungal DNA.

Of the 37 ice pops, three had Penicillium present and all had high levels of galactomannan. Although the source of the galactomannan in the ice pops could not be nailed down because of a lack of detailed information about the production process, food additives containing galactomannan are one possibility, according to the researchers.

"One possible source is sodium gluconate, which is currently used in Europe and the U.S. as a thickener and stabilizer for water-based frozen desserts and is known to cause false-positive tests for galactomannan," they wrote.

"In our patient," they added, "a mucosal translocation of galactomannan after consumption of the flavored ice pops is a plausible explanation."

Guigue reported that he had no conflicts of interest. His co-authors reported relationships with Bio-Rad, Pfizer, Merck, and Gilead.

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